1. Technical Field
The present invention relates to a projection-type display device such as a projector and a method of controlling thereof.
2. Related Art
As is widely known, a projection-type display device such as a projector is a device that includes a light source, an optical modulation device, and a projection lens and displays an image on a screen by modulating light emitted from the light source by using the optical modulation device and projecting the modulated light onto the screen by using the projection lens. Generally, projectors include a lamp such as a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp as the light source. However, recently, projection-type display devices including solid-state light sources such as an LD (Laser Diode) and an LED (Light Emitting Diode) have been actively developed.
Here, the above-described various lamps used as light sources of the projectors have characteristics that the lamps are extinguished at a time when an applied voltage is lower than a specific voltage and it takes a long time (for example, several minutes or more time) for the lamps to be relighted. Accordingly, in a general projector including such a lamp, a circuit is arranged which is used for maintaining the lighting state of the lamp for an interval (for example, about one second) of some degree even in a case where an instant interruption (instant voltage drop) of the power source occurs.
In JP-A-2004-303507, a device is disclosed which decreases a current output from a converter circuit by changing PWM (Pulse Width Modulation) control for the converter circuit so as to avoid rapid consumption of interlay-stored energy in a case where an input voltage is lowered to be equal to or lower than a predetermined value, thereby maintaining discharge of a lamp. In addition, in JP-A-2002-367791, a device is disclosed which performs a countermeasure of an instant interruption by decreasing the power supplied from a capacitor to a discharge lamp based on a detection result of an instant interruption detecting unit that detects an instant interruption of the power source.
However, a solid-state light source, differently from the above-described various lamps, has characteristics that it can be instantly relighted by supplying a predetermined current used for lighting the solid-state light source even when the applied voltage is lowered to zero [V]. Accordingly, in a projector including a solid-state light source as a light source, unlike JP-A-2004-303507 and JP-A-2002-367791, it may be thought that control of continuously supplying minimum power necessary for lighting the lamp to the lamp in a case where an instant interruption occurs is unnecessary, and a circuit used for maintaining the lighting state of the lamp is unnecessary.
However, in a case where the circuit used for maintaining the lighting state is omitted in the projector including the solid-state light source, the display of an image on a screen is stopped when an instant interruption occurs, and there is a concern that a user may erroneously determine that the projector is out of order. In addition, in order to redisplay the image that has been stopped due to the instant interruption on the screen, the user needs to input power to the projector again, and accordingly, the user is compelled to perform an inconvenient operation. Considering such problems, also in the projector including a solid-state light source, the circuit used for maintaining the lighting state in a case where an instant interruption occurs needs to be included.
Here, the circuits disclosed in JP-A-2004-303507 and JP-A-2002-367791 described above need to continuously supply minimum power necessary for lighting the lamp to the lamp when an instant interruption occurs. Accordingly, there are problems in that the efficiency is low, and the period during which lighting can be maintained is limited. In addition, since the power supplied to the lamp is not allowed to be equal to or lower than the minimum power, there is a problem in that a countermeasure in which the lighting period is lengthened by performing precise control cannot be performed.